Related Experiment Video
Updated: Jul 2, 2025
A Human Peripheral Blood Mononuclear Cell PBMC Engrafted Humanized Xenograft Model for Translational Immuno-oncology I-O Research
Published on: August 15, 2019
A peripheral blood mononuclear cell-based in vitro model: A tool to explore indoleamine 2, 3-dioxygenase-1 (IDO1)
Milene Gonçalves1, Alessia Furgiuele2, Emanuela Rasini2
1Univ Coimbra, Coimbra Institute for Clinical and Biomedical Research (iCBR), Faculty of Medicine, Coimbra, Portugal; Univ Coimbra, Institute of Pharmacology and Experimental Therapeutics, Faculty of Medicine, Coimbra, Portugal; Univ Coimbra, CIBB - Centre for Innovative Biomedicine and Biotechnology, Coimbra, Portugal; Clinical Academic Center of Coimbra (CACC), Coimbra, Portugal; Univ Coimbra, Institute for Interdisciplinary Research, Doctoral Programme in Experimental Biology and Biomedicine (PDBEB), Coimbra, Portugal.
Background:
Proinflammatory cytokines powerfully induce the rate-limiting enzyme indoleamine 2, 3-dioxygenase-1 (IDO-1) in dendritic cells (DCs) and monocytes, it converts tryptophan (Trp) into L-kynurenine (KYN), along the kynurenine pathway (KP). This mechanism represents a crucial innate immunity regulator that can modulate T cells. This work explores the role of IDO1 in lymphocyte proliferation within a specific pro-inflammatory milieu.
Methods:
Peripheral blood mononuclera cells (PBMCs) were isolated from buffy coats taken from healthy blood donors and exposed to a pro-inflammatory milieu triggered by a double-hit stimulus: lipopolysaccharide (LPS) plus anti-CD3/CD28. The IDO1 mRNA levels in the PBMCs were measured by RT-PCR; the IDO1 activity was analyzed using the KYN/Trp ratio, measured by HPLC-EC; and lymphocyte proliferation was measured by flow cytometry. Trp and epacadostat (EP) were used as an IDO1 substrate and inhibitor, respectively. KYN, which is known to modulate Teffs, was tested as a positive control in lymphocyte proliferation.
Results:
IDO1 expression and activity in PBMCs increased in an in vitro pro-inflammatory milieu. The lymphoid stimulus increased IDO1 expression and activity, which supports the interaction between the activated lymphocytes and the circulating myeloid IDO1-expressing cells. The addition of Trp decreased lymphocyte proliferation but EP, which abrogated the IDO1 function, had no impact on proliferation. Additionally, incubation with KYN seemed to decrease the lymphocyte proliferation.
Conclusion:
IDO1 inhibition did not change T lymphocyte proliferation. We present herein an in vitro experimental model suitable to measure IDO1 expression and activity in circulating myeloid cells.
